Sweep generator



Sept. 26, 1950 D. M. JACOB 2,523,753

SWEEP GENERATOR L Original Filed Jan. 30, 1945 2 Sheets-Sheet 1 PULSER Fig.4.

Inventor" Don M. Jacob,

His Attorney.

Sept. 26, 1950 M, JAG QB 2,523,763

SWEEP GENERATOR Original Filed Jan. 30, 1945 2 Sheets-Sheet 2 4, Fig.6.

PULSER a v I PU LSER 8 PULSER 1- Inventor: Don MJac ob His Attorney.

Patented Sept. 26, 1950 UNITED STATES "SWEEP elimination Don Jaco'b, S'chenectady, assi ner to :General- Electric .-;Company, :a rsccrporaticn 16f Newj york Original; appl cati n January 20. 19425, Se l it 575,309. Divided and this*applicatioh Apri-l--30,

.This invention relates .tospulse ;.eChO :systems and means for calibrating certain ;of .the;indieating devices in such "systems, and more particularly to .a sweep generator sadapted...ior..use 111 :such devices.

Pulse echo systems. have .been. proposed forqthe determination of the range and-relativervelocity of a desired object. Such systems .areyuseful on moving objects, such as aircraft and.ships,..for studying the relativennotioniof other. moving-objects, or for indicatingxtheapproach of :amoving object to a fixed .obiect. .Thus, it may .:be desired to determine the relative speed :between relatively nearby aircraft .and :also to determine whether the distance between them .is becoming less or greater. For the satisfactory operation of such systems, it is necessary to haveavailable testing equipment for calibrating accurately the indicating instruments associated :with the pulse echo system.

It is an object of .myinvention top-providacalibrating or testing equipment-zcapable'of checking either the range or relative velocity indicators, or both, in pulseechosystems andia.more specific object is to provide a. sweep zgenerator .whichwill operate at high frequencies useful in.. such 'equip- .ment.

The features of my invention -.whi'ch;-I.be1ieve to be novel are set forth withgparticuiarity. in the .appended claims. My invention :itself, both. as to its organization and" manner :of operation, together with further objects and advantages thereof, may best be understood by reference .to thefollowing descriptionataken in connection with the accompanying drawing in which Fig.1 isa schematic diagram of :the circuits-{constituting-one embodiment of my invention, Figs. 2.110 5-inc1usive are diagrams illustrating operating/characteristics of the circuit .illustrated' in Fig..1 ,.Fig.. 6 is a second embodiment of my invention,-..Fig. 7, is a modification of thecircuit shown in Fig. ,6, and Fig. 8 is still another embodiment .of my invention.

In accordance with my invention, there is progating.,.-'means 5:2 :for. i 'tiating .:-operation- :of :the -fast sweep. ggeneratorsinresponse to; suitable isynic-hronizing pulses. received-from. theithepulse' echo system. 'Iihe-vnltage obtainedfrom the fastsweep 5 generator-is impressed uponza trigger ;device..3

twhichJ-in turntriggerma,suitable .pulsing device -4. The rartificialyta'rget.pulsesemitted. from the ggpuls'er (are, impressed. on the; =pu1se-echdsystemto be calibrated.

ties \a-reiof 1 the .eor'der of 100::and 500 :milestler hour .away-sfrom or itoward fthe "reference .point whi'ch.in;;practica1 -operation;.;is .thezsidecof the :pulse eehdequipment. In:;0r der .tocchoosecthe approximate rate and direction of travel; there. is

.provided-.-. a= two ;.arm, switchs5 havinguplus fand iminus 100 miles ;-per :hour positions and plus 5, and minus @500 :miles :'per ;=hour;=positions, the terms .plusand :minus referring to. therrela-tive approach and recession, respectivelyrrof the objects ainvolved. flhapositionof -switch 5 determines the is provided a fractional. velocityrrmultiplierior 500111301 :6 -showniin1 the-dormer-ai=potentiometer.

When theaa-rmcofthe potentiometer engages one 7 end:of the resistance the velocity. is minimum and when the arm-is at the otherzend of 'theresistance the velocityv is thev-maximumfor the setting of switch-=5. ;In -.oper-ation, assuming; power issuitably :connecte'd- 113.0 theucircuit, andoutput leads at i and. inputrleadfi are-suitably connected :to the equipment-tome: tested-the relative velocity; con- .t-rol s isturned-tothe desired position. 7 For pur-.

:;poses of :description,.-.1et -it. -.be-. assumedthat; the

40 vswitch-ta is turn-ed to.-;the;p1us'=500 :miles per hour position-Lasindieate'dzinFig. I The velocity multi 'plier potentiometer;{6 :is set toe; position corresponding --to: therabsolute "velocity. to be. calibrated as, for example-1350 miles-perhour. Thereis provided calibrating apparatus which provides -.-a-n: ,45 videdzan-initial .ra-ngecontrpl: H! which is operartificial target pulse which can be made to move over a wide range of relative distancesat awide range of relative velocities with respect-:tozan external input synchronizing pulse derived from the pulse echo system being calibrated.

Referring to Fig. 1 of the drawing,.-there ;is provided a fast sweep generator I to :whichrmy invention particularly pertains arrangedstoygenerate a timing wave at a recurrencera'te ofathe atedtuntil the,pulse-echo"equipment being cali- '.--bra-ted.1ocks aonthe (artificial target pulse from the pulsing-device i4. -.-Undert ;these conditions the range :indicator :of, thejpulse echo requipmenty'now 11.50 .yaries. a the range of the artificial target: changes.

.-Hold down switch r H v is then; pressed, making operative,the;slow.sweep generator to modify the I biasz' or threshhold:of.the-trigger.devicer3. ,;By reason of changing 'ibias-zdu-ring the operative order of microseconds. .There. isv alsoyprov'ided.,55.periodofthesecond'isweengenerator as herein- The' 'cir'cuit shown .-in Fig.;- 11I.is .designed to. brate veloci-tiesattwo levels. The,.:absolute values. of the velocities will depend uponthe yalueszofafter explained, the target indication will move in the selected direction (toward the operator for conditions as illustrated in Fig. 1) at a selected rate (determined by the relative velocity switch and velocity multiplier potentiometer 6).

Describing my invention in greater detail, the fast sweep generator i includes an electron discharge device illustrated as being of the pentode type having an anode i2,a cathode I3,control electrode I4, screen grid electrode [5 and suppressor grid 16. The anode i2 is connected to a suitable source of positive potential, the negative terminal of said source being grounded. The screen.

electrode I5 is connected to a suitable source of potential through a suitable voltage limiting resistor H. The cathode I3 is connected to the upper end of a cathode bias resistor is. The suppressor grid 16 and control electrode l4 are connected together and to the lower end of resistor Hi. In order to maintain relatively constant the potential on screen electrode l5 with respect to the cathode, there is provided a capacitor [9 connected between the screen electrode I5 and the lower end of resistor l8. In series with the above-described electron discharge device, there is a second electron discharge device which may be a suitable double-triode type having anodes 2i and 22, control electrodes 23 and 24 and cathodes 25 and 26 respectively. The cathode i3 is connected to the anode 22 through the bias resistor l8 and the initial range control it! including potentiometer 27. The cathodes 25 and 26 are connected together and to ground through a bias resistor 28. The control electrode 24 is connected to the anode 2| through a suitable capacitor 29. The two sides of the electron discharge device 20 are connected together for multivibrator operation with the right hand side normally conducting and the left hand side normally cut off. When a sufiiciently positive synchronizing pulse from the pulse echo system is impressed upon the control electrode 23, as by means of a suitable coupling capacitor 36, multivibrator action quickly renders the left side conductive and the right side of electron discharge device 20 nonconductive, the control electrode 24 having been driven sufiiciently negative to out 01f the discharge current.

The relative velocity switch 5 comprises a pair of switch elements SI and 32 having switch arms arranged to engage a plurality of contacts as indicated in the drawing. As briefly explained heretofore there are four switch positions. The first position represents a negative velocity of 500 miles per hour, the second position represents a negative rate of 100 miles per hour, the third position represents a positive rate of 100 miles per hour and the fourth position (indicated in the. drawing) represents a positive rate of 500 miles per hour. The switch arm of switch element Si is connected to a suitable source of positive potential and also to one side of capacitors 33 and 34. The negative and positive 500 miles per hour contacts of switch element 3| are connected together and to one side of capacitor 35. The other sides of capacitors 33, 34 and 35 are connected together and to anode 22 and the lower terminal of potentiometer 21. Thus, when the relative velocity switch 5 is in one of the 500 miles per hour positions all three capacitors are -con-- nected in parallel to the source of positive potential whereas in the 100 miles per hour position of the switch only capacitors 33 and 34 are connected to the source of potential.

When the right hand side of discharge device 11 2c is conducting, the capacitors connected in the circuit become charged. At the instant that discharge device 20 is cut off, the lower sides of capacitors 33 and 34 (and capacitor 35 in either of the 500 miles per hour positions) are at the potential of the positive source and the upper sides of the capacitors are at the potential of anode 22. While the right hand side of discharge device 20 is cut off, the potential of the upper sides of the capacitors rises substantially linearly toward that of the lower side. That is capacitors 33 and 34 discharge throughpotentiometer 2'7 and the constant current path including cathode l3 and anode I2 to the potential of the positive terminal of the potential source.

The action thus far described is indicated graphically in Fig. 2. At line A there are illustrated representative positive synchronizing pulses from conductor 9. Line 13 represents the potential at the upper sides of the capacitors 33 and 34 and hence, at the anode 22 of discharge device 20. When the right side of discharge device 20 again becomes conductive, the potential at the upper sides of the capacitors falls to its normal value and the sweep generator and gating means are conditioned for the next synchronizing pulse.

The trigger device 3 comprises an electron discharge device 36 of a suitable double triode type although two separate suitable electron discharge devices may be used. The right hand side acts as a cathode follower and normally conducts current of magnitude depending upon the potential appearing at the control electrode 3?. This potential is determined by the setting of the relative velocity switch 5. The anode 38 is connected to a suitable source of positive potential. The cathode 39 is connected to ground through a suitable bias resistor 40. The cathode 4! of the left hand or trigger side of the discharge device 36 is connected to cathode 39 and the upper end of resistor 40. The anode 42 is connected to the pulsing device 4. The control electrode 53 is connected to the arm of the potentiometer 27 through a suitable potential limiting resistor. In order to minimize the efiect of the grid-cathode capacity in the left hand side of discharge device 36, a suitable capacitor 44 is connected between anode 22 and control electrode 43.

As the potential at the lower end of potentiometer 21 increases, the potential at the control electrode 43 increases proportionately. Eventually, depending upon the bias established for the trigger device, the left hand side of device 36 conducts current. Thus, at a certain delay time after the synchronizing pulse'is applied to control electrode 23 of discharge device 2G, a. time interval depending upon the setting of the potentiometer 2? and the bias of the left side of discharge device 36, a trigger pulse appears on anode 42 as indicated at line C in Fig. 2 which results in the emission of an artificial target pulse from the pulser 4 as indicated at line D in Fig. 2.

The apparatus thus far described is sufficient to calibrate the range indicator of a pulse echo system. For example, a range within the limits of the pulse echo system and the calibrating device is selected by properly adjusting potentiometer 21. Assuming connection of the calibration device to the pulse echo system, the artificial target pulse should appear at the chosen range mark on "the pulse echo equipment. In order to check difierent ranges, it is simply necessary to change the setting of potentiometer 2?. In .a typical embodiment of this circuit, capacitors 33, 34 and positive potential.

-;;5 65 are so chosen that the rang coverage with switch 5 in the 100 miles per -hour setting is approximately 400 to 4000 yards and in the other setting approximately 1000 to 18,000 yards. In some cases, the entire desired range may be covered with onlyone value of capacity but where an extended range coverage is required, more satisfactory results are obtained if sever al 'con- -densers are used because :of improved accuracy obtained, and minimum voltagesource require- =ments.

In order to calibrate that portion aofthelpulse e'ch'o system used for checking thezrelative velocities of moving objects, there is provided means iior continuously, andpreferablyllinearly, varying the threshold on the trigger :side of discharge device -36 in either the positive or negative'direction. For this purpose, there is providedthe slow sweep generator 1 having a period of recurrence of the order of seconds (it will be recalled that the period of recurrence of the fast sweep @gen- .erator is of the order of microseconds). The voltage derived from the slow sweep generator is applied to the control electrode '31 of electron discharge device 36. Any change in the bias of control electrode 3'! varies the current through the resistor 40 and hence the threshold of the left hand side of electron "discharge device 36. Accordingly, it will take a shorter or longer time for the linearly increasing voltage applied to control electrode 43 to overcome the threshold depending upon the direction inwhich the potential of control electrode 3! is changing.

The illustrated slow sweep generator includes an electron discharge device Q5 which may be of *a-suitable double triode type. The "anode 46 of the right hand side is connected to a suitable source of positive potential through the-positive range set control 63 illustrated in the -form of a variable resistor. The cathode 41 is connected to ground through a suitable bias resistor :48. The control electrode 49 is connected to ground through a resistor 50 and normally closed hold down switch I l. A suitable capacitor 5| is connected between anode 46 and the junction between resistor 50 and hold down switch II. The .junction between hold down switch II and ca- -,pacitor 5| is connected to a suitable source of With this arrangement, the control electrode 49 is normally grounded through the switch I I. When it is desired to initiate operation of the slow sweep generator, hold down switch II is pressed thereby opening the circuit from grid to ground. As soon as the switch i l is opened the lower side or capacitor 5! is released from ground and the capacitor 5| begins to charge substantially linearly until the switch is'releas'ed, thereby again grounding the capacitor, or until 'grid current flows in the right hand side of discharge device 45. The potential on control electrode 49 follows the voltage on the lower side of capacitor -5| so that as this voltage increases linearly, the current flow through the right hand side of discharge device 45 increases proportionately. As a result, the potential of anode 46 decreases linearly and therefore a linearly decreasing voltage appears on the arm-f velocity multiplier 6. The arm of the velocity multiplier potentiometer is connected to control electrode 52 of the left hand or phase inverter side of "voltage causes the potential on control electrode 8-1 of discharge device 36 to decrease whenever th switch 32 is engaging"l-theEpositivenate3c6n- As a resultg'with switchi5 in th'eip'osition shorter'intervals, .aslong as the hold .down'switch' I is held open or until-grid current fiowsl'initlie righthand side of discharge device 45.

Fig. 3 represents the effect of holding op'entthe switch I l for difierent lengths of time." zIn-qa typical embodiment of my 'inventionapp'roxi- =rri'ately' 40 seconds" is required to cau'selgrid current to flow in the-right hand-iside -'of discharge "device' 45, The "full line' in Fig.3 is represent'ative -"of'=the condition where the "switch H held open for :30 seconds. If the switch 'is held open only :15 seconds, therchargingyoltage follows the same line but haltsTsoonerand at'a lower mean- "mum amplitude as indicated by the dashed-line.

In Fig. 4 the line 53%repres'ents the continuously.

andllinearly decreasing voltage appearing-at control electrode :31.

The'anode 54'ofthe left hand or"phaseinverter side of discharge device 15 4s connected to "a suitable source of positive-potential and zto the negative switch contacts of switch '"element 32 through a suitable voltage limiting "resistor.

cathode "55 'is connected to "ground through a suitable bias resistor 56. As the voltage oncontrol electrode 52 decreases, as explained above, the current through -the left hand rsidefof discharge-device 45 decreases whereby thevpo'tential "o'f anode :5 i increases-"continuously "and substan- 'tially' linearly as indicated by the line" 51 in Fig-*4. 'Whenever the switch-"armof switchelement 32 is turned to 'a position inwhich'theswitcharm engageseither of the negative rate c'ontacts, the

'p'otential'on contr'el electrode .3 will continii- 'ously' a'nd linearly "increase in the positive directioh, whe'ntswitch ll isopend, "causing'a'continuous increase in current through the right handside of discharge device 36, a continuous tive potential of the potential-impressed on the control electrode 3! 0f the right hand side or discharge device 36 and therefore in accordance with the direction in-and extent to which the threshold is modified when the slow sweep generator is operative. Fig..-5 depicts graphically the Variation 'in trigger time er the-discharge;

device 36. 'Time "relationships 'h'aV'e Ebe'en "distorted to illustrate clearly operating 'ch'a'racteristicsl The line 58 represents the sweep voltage applied to control "electrode l'e :as a result ofthe operation of'the fast sweepigenerator and gating mea'ns. The :line .59 represents a gradually increasing threshold at the left hand side of dis chargezdeVice 36. Line 60 represents theinorrnal thresholdizor cut-off :bias the left ihandlisi'rle The of discharge device 36. Line 6! represents the resulting variation of potential on control electrode 33 of discharge device 36. Whenever the resultant effective control electrode potential crosses the cut-off line, represented by the numeral 60, the trigger device is rendered operative. It will be noted that as time passes, the intervals between successive periods of energization of the left hand side of device 36, as indicated by A and B in Fig. 5, becomes less and less. If the switch is in one of the negative rate positions, a similar analysis would show triggering at greater and greater intervals as the hold down switch is operated.

Means is provided to make the intial range of the artificial target pulses independent of the setting of velocity multiplier 6. That is, with switch ll closed variation of the position of the movable contact on potentiometer 6 should not affect the potential on grid 31 of device 36 or the bias voltage on resistance irrespective of the position of switch 5. This is accomplished by adjusting the voltage on the anode 46 to the 'same amplitude as that on the lower end of the velocity multiplier 6. With such an arrangement, variation of the arm of potentiometer 6 will not upset the voltage relationships on the left hand side of discharge device and the starting po-- tential i. e. the potential when switch I! is first opened, on the movable arm of velocity multiplier 6 will always be equal to the potential on anode A6, assuming proper adjustment of resistor 63.

In order to provide, at any given range, the

same rate of change of relative velocities for approach and recession tests, there is provided an adjustable resistance 32 connected between the negative contacts of the switch element 32 and the arm of the potentiometer comprising the negative rate range set control 64. The same starting voltage at switch 5 may be obtained for the positive and negative directions of relative velocity by changing the negative rate range set control 64. In other words, the starting voltage on the negative rate contacts of switch element 32 is determined by the setting of potentiometer 64 and negative rate calibration resistance 62. The starting voltage on the positive contacts of the switch element 32 depends upon the setting of the resistor 63 and the velocity multiplier 6, assuming that the voltage across control 6 has been properly adjusted to zero.

In order to compensate for the different cathode currents obtained in resistor 28 of gating means 2 in the 100 and 500 miles per hour positions of switch 5 and provide equal bias for the left hand side of device 26 in all positions of switch 5, there is connected between cathode 26 and the lower end of capacitor 35 a suitable resistor 65. This resistance passes current from the positive terminal of the source of operating potential to ground through resistance 28 to produce increased bias thereon when switch 5 is in those of its positions where the bias on this resistance produced by current flowing through tube 20 is smaller. The bias on resistance 28 is produced in part at least by current flowing in grid 24 and through the different grid resistors to the positive terminal of the source of operating potential. These resistors have values chosen in accord with the desired rates of variation of the rise in voltage represented by curve B. Since they are unequal, unequal currents flow in the grid when switch 5 is in different positions. Resistance 65 is chosen to make the bias on resistail 8 ance 28 equal in all positions of the switch notwithstanding the unequality of the current flowing in tube 20 for different positions of the switch.

Fig. 6 shows a modification of my invention arranged for range calibration only. With this arrangement the slow sweep generator and velocity multiplier are omitted and the trigger device is simply a triode 66 connected for operation in the same manner as the trigger or left hand side of trigger means 3 in Fig. 1. The switch element 32 of relative velocity switch 5 is also unnecessary. The operation is the same as the corresponding portion of Fig. 1'.

Fig. '7 illustrates an improvement over the embodiment shown in Fig. 6. In this modification the double triode 36 of trigger means 3 is employed in the same manner as shown in Fig. 1 except that the control electrode 31 of the right hand side of electron discharge device 36 is connected to the junction between capacitor 19 and the upper end of range control [0 instead of being connected to the switch arm of switch element 32 of Fig. 1. With this arrangement any voltage variations in the fast sweep generator will be compensated for whereby the range indicator will be more accurate than with the arrangement shown in Fig. 6. Any variation in voltage on the lower side of capacitor I9 is impressed upon control electrode 31. Since the right hand side of device 36 is connected as a cathode follower, any changes will be reflected in compensating changes in bias at resistor 40. For example, if the voltage at the lower end of capacitor l9 decreases, the effect without the connection to control electrode 37 is to decrease the potential impressed on control electrode 43 and, hence, the triggering of the pulsing device 4 is delayed. However, with the connection of Fig. 7, the decrease in voltage results in a decrease in current through the right hand side of discharge device 36 causing a decreasein current through resistor 46. There results a lowering of the threshold on the left hand side of the discharge device so that a lower potential on control electrode 43 is required to cause conductivity through the left hand side of the electron discharge device. Of course, the abovedescribed connection can also be made inthe circuit of Fig. 1 with improved stability.

Fig. 8 illustrates a second embodiment of the invention disclosed in Fig. 1. Referring again to Fig. 1, the effect of approach and recession of target was accomplished by providing an increasing or decreasing potential on control electrode 31 of discharge device 36. The same general effect may be achieved by employing a switch 67 arranged to impress either a positive or a negative potential on control electrode 49 of the slow sweep generator. In this embodiment of my invention, the variable resistor 63 is omitted so that the normal potential across the velocity multiplier 6 is not zero as was the case in the circuit of Fig. 1. Hence, the normal potential on control electrode 31 of discharge device 36 of Fig. 1 is no longer zero when the hold down switch I! is in its closed position but is some positive value, the actual amplitude depending upon the position of the arm-of the velocity multiplier. Therefore, whenever the position of the velocity multiplier is adjusted the range control I0 must also be varied to compensate for the change of level in potential. If desired, the

range control In and; velocity multiplier 6. may" be ganged together;

The slow sweep generator describedherein is: described and claimed in the copending application of Philip C. Michel, Serial No. 576,567, filed Januar 30, 1945, and now Patent No. 2,460,142, while the complete calibrating system. and certain aspects of the slow sweep generator'are'described and claimed in my copending application Serial No. 575,309, filed. January 30, 1945, or which the present application is adivision.

Both of these applications. are assigned to.- the assignee hereof.

While I have shown and described arparticular embodiment of my invention, it will be ob.- vious to those skilled in the: art that changes and modifications may be made without departing from my invention in.- its broader aspects, and. I therefore aim in the appended claims. to cover all such changes and modifications as fall with-- in the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A sweep generator comprising asource of direct current potential, a capacitor, one side of said capacitor being connected to the positive terminal of said. source of potential, an electron discharge device comprising a cathode, an anode and a control electrode; a' resistor connected to said cathode, said control electrode being connected to an intermediate point on said resistor, and the anode-cathode path of said device and said resistor being connected in series across said.- capacitor, the anode of saiddevicebeing connected to the positive terminalof said source, switching means connected between the other side of said capacitor and the negative terminal of said source of potential for causing said capacitor to charge. whensaid switching means is electrically conductive. and to discharge through said resistor and anode-cathodepath whenzthere is no electrically conductive circuit through said switching means whereby the potential on said other side of said capacitor rises substantially linearly thereby causing a change in potential of said resistor.

2. A sweep generator comprising a source of direct current potential, a capacitor, one side of said capacitor being connected to the positive terminal of said source of potential, an electron discharge device comprising a, cathode, an anode and a control electrode, a resistor connected to said cathode, said control electrode being connected to an intermediate point on said resistor, and the anode-cathode path of said device and said resistor being connected in series across said capacitor, the anode of said device being connected to said positive terminal, switching means connected between the other side of said capacitor and the negative terminal of said source of potential for causing said capacitor to charge when said switching means is electrically conductive and to discharge through said resistor and anode-cathode path when there is no electrically conductive circuit through said switching means whereby the potential on said other side of said capacitor and on said resistor rises substantially linearly, said switching means comprising an electron discharge device arranged to be normally conductive and means for rendering said last discharge device nonconductive.

3. A sweep generator comprising a first electron discharge device having an anode, a cathode; ascontrol electrodeand a; screen electrode.

said anodebeing connected directly to a-sourcei of. positive; potential, meansto maintain. said.

screen-'- electrode' at. asubstantially constant,

positive potential with respect 'to said cathode, a.

secondelectrorr discharge: device having. an an, ode; a cathode anda control electrode, said lastj mentioned. cathode.- beingconnected toground: through: a. bias. resistor, voltage dividing meansconnected between the cathode or saidfirstdis-s charge device and the anode of said second-.discharge device; said.;first-mentionedcontrol electrode being connectedt-toa: predetermined point! insaid-s voltage dividing. means, said. discharge.

devices being arra-ngedto be normally-conduct ing, .a-icapaeitonconnected between the anode of: SaidPsecOnd. device and the anode of-- said first.

device, and-meansfor. rendering said second dist-- charge device noneconducting' to change ofpotential on said. capacitor whereby the-potential with respect: towground potentialtofsaid voltage=dividing-means varies according to the: changeof-xpotential on said. capacitor.

4; Asweepgenerator'comprisinga a first electron discharge device including an anode-,-' a:

cathode,- a'controlf. electrode, and: a screen electrode, said anode'being; connected: to 'a-source ofpositive-potential, a second electron. discharge device having; an anode; a cathode: anda con trolelectrode, the last-mentioned cathode being. connected, to ground. through a biasresistor, voltage dividing means? connected between/the cathode: ofisaidfirst discharge device and the.

anode ofzsaid; secondi: discharge device, said corr trol electrode: of. said first device being con-- nected: to anrintermediate-point in said means, said: discharge--devices being-arranged to be. nor:-- mally conducting; a capacitor connected be.--

tweenzt-hes anodezof said second device and-.the

anoderof said; firstvdevice, means for rendering; saidrsecond: discharge; device non-conducting to: initiate a change of potential on said capacitor whereby the potentialon said voltage dividing means varies according to the charge on said capacitor, a second capacitor connected between the screen electrode and the cathode of said first discharge device, and means to bias said screen electrode positively, whereby substantially constant voltage is held at said first discharge device and substantially constant current is maintained in said sweep generator.

5. In a saw-tooth wave generator, a source of directcurrent potential, a capacitor, a connection from one electrode of said capacitor to a terminal of said source, a normally conductive connection between the other capacitor electrode and the other terminal of said source, meansoperable abruptly to increase substantially the impedance of said last connection, means connected between said electrodes in series with a resistive impedance for maintaining a substantially constant current to discharge said capacitor upon operation of said first means, and adjustable means for obtaining an output voltage from a desired adjustable poi t on said resistive initiate: a

conduction and said second device to non-conduction, the anode-cathode discharge path of said first device being interposed in circuit between the other capacitor electrode and the other terminal of said source, means for providing a discharge connection of substantial impedance from said'other electrode to said one terminal, and means for triggering said lmultivibrator, said means for providing a discharge path being effective to discharge said capacitor upon operation of said last means.

7. A saw-tooth wave generator comprising a source of direct current potential, a capacitor with one electrode connected to one terminal of said source, means for maintaining said capacitor charged comprising a multivibrator with a normally conductive electron discharge device, said device being in circuit from the other electrode of said capacitor to the other terminal of said source, said multivibrator comprising means for triggering said device to non-conduction, and a discharge circuit operative upon triggering of said device to non-conduction to provide a conductive path from said other electrode to said one terminal.

8. A saw-tooth wave generator comprising a source of direct current potential, a capacitor with one electrode connected to one terminal of said source, means for maintaining said capacitor charged comprising a multivibrator with a normally conductive electron discharge device, said device being in circuit from the other electrode of said capacitor to the other terminal of said source, said multivibrator comprising means for triggering said device to non-conduction, and

a discharge circuit operative upon triggering of said device to non-conduction to provide a conductive path from said other electrode to said one terminal, said discharge path comprising in series from said electrode a resistor and means tending to maintain a constant current through said resistor to said one terminal, whereby the amplitude of the saw-tooth voltage wave is substantially the same at all points on said resistor.

9. A saw-tooth wave generator comprising a source of direct current potential; a capacitor with one electrode connected to the positive terminal of said source; means for maintaining said capacitor charged comprising a multivibrator with a normall conductive electron discharge device, said device being in circuit from the other electrode of said capacitor to the negative terminal of said source, said multivibrator comprising means for triggering said device to non-conduction; a resistor and second electron discharge device connected in series in the order recited from said other electrode to said positive terminal, said second device having a cathode connected to said resistor, an anode connected to said positive terminal, and a control electrode connected to a point on said resistor other than the cathode end thereof whereby said second device provides a conductive path of high alternating current impedance; and adjustable means for connecting an output terminal to a desired adjustable point on said resistor to obtain the linearly varying voltage appearing at all points on said resistor with a desired direct current bias when said first discharge device is triggered to non-conduction. DON M. JACOB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,155,210 Young Apr. 18, 1939 2,195,972 Pieplow Apr. 2, 1940 2,275,460 Page Mar. 10, 1942 

